This invention relates generally to vacuum processing apparatuses and more particularly to a vacuum processing apparatus in which the temperature of a substance or an article being processed within a vacuum vessel can be controlled accurately and positively within a short time.
Various vacuum processing apparatuses have been and are being developed for processing articles or materials to be processed (hereinafter referred to as "work"), such as semiconductor wafers, within a vacuum chamber, examples of such processes being etching, sputtering, ion injection, plasma CVD, electron beam irradiation, and vapor deposition.
For example, when work such as a semiconductor wafer is to be vacuum processed with a gas plasma, the work is cooled in order to protect its resist film. In this case, when the processing is to be carried out at a low processing power density, for example, of 0.3 W/cm.sup.2 or less, it is suffient merely to place the work on a specimen table which is being cooled.
On the other hand, in the case of processing at a high processing power density (of 0.3 W/cm.sup.2 or higher), use is made of means for cooling by mechanically pressing the work against the specimen table being cooled. In another cooling method being practiced, a narrow space is formed between the specimen table and the work and is sealed by means such an an O ring, and, while a cooling gas is introduced into this space, the work is mechanically pressed against the specimen table.
Furthermore, a recently proposed vacuum processing technique comprises interposing a dielectric film between the cooled speciment table and the work, providing a direct-current electric circuit formed by utilizing the electroconductive property of a gas plasma, and imparting a potential difference between the specimen table and the work thereby to cause the work to be drawn firmly on the dielectric film against the specimen table (as disclosed in Japanese Patent Application Publn. No. 53853/1981).
However, in the practice of the above described technique, although no problem is encountered as to cooling capacity during low-power processing, the problem of insufficient cooling has arisen in the case of high-speed processing at a high power density of, for example, 0.8 W/cm.sup.2 or higher.
Furthermore, in the process of cooling the work as it is mechanically pressed as described above, there is the risk of an excessive load being applied to the work. Moreover, since non-uniform parts of the pressing device contact the work, they impart a deleterious effect on the work, and dust tends to infiltrate into the interfacial space between the work and the pressing member.
The technique of forming a narrow space between the specimen table and the work, pressing the work mechanically against the table, and cooling the same with a cooling gas has heretofore entailed the risk of damaging the surface of the work. A further problem has been the difficulty of carrying out uniform processing due to the difference between the impedances of the gas-cooled parts and other parts of the work.
In addition, in the technique of causing the work to adhere to the specimen table over a dielectric film interposed therebetween, also, there has been a problem of difficulty of cooling or heating the work to a specific temperature because of lowering of the thermal conductivity due to the formation of a vacuum layer in the interfacial interstice between the opposed surfaces of the specimen table and the work. This interstice inevitably exists as a consequence of the fact the opposed surfaces are not perfectly planar surfaces.